1. Field of Invention
The present invention relates to rotary drill bits particularly bits of the drag type having provision therein for transmitting through a head portion of the drill bit a fluid which during the course of drilling is utilized both to cool the cutting edges and to conduct cuttings to the surface.
2. The Prior Art
It is conventional to drill bit technology to provide means in the drill bit for circulating fluid to the bottom of the well being drilled. Thus the prior art is replete with drill bits having means for circulating fluid to the bottom of the well being drilled so that the cutting blades or edges of the drill bit may be lubricated and cooled by the fluid and the cuttings carried upward by the fluid to preclude sticking of the drill bit by such cuttings.
An exemplary drill bit of the drag type is described in U.S. Pat. No. 3,163,244 to R. D. Zimmerman. Fluid from central passage 50 exits by way of passages 52 into the wellbore where it follows two paths, one downward for cooling the cutting edges and the other upward for carrying cuttings to the surface.
Another patent illustrating a drill bit with means for circulating fluid to the bottom of the well is U.S. Pat. No. 2,950,089 issued to R. D. Irons. In this patent flow of fluid out of passage 20 is directed downward by way of aperture 24 in a deflector having a web portion 23 and upward by way of an extended side flange 25.
In all cases the apertures which direct the fluid toward the bottom of the well being drilled for purpose of cooling the cutting surface are subject to being clogged by cuttings and other debris as pressure is exerted upon the drill bit while making hole. As a result the cutting surfaces begin to over heat and wear more rapidly. In some instances the apertures by which the fluid is emitted from the center of the bit are completely clogged thereby preventing cuttings from being carried to the surface.